QED Environmental Systems is the leading manufacturer of innovative environmental products.
For over 30 years their expertise has included Pumping Systems, Landfill Products, and Air Strippers.

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QED Air Stripper Fouling Tool

Enter water parameters to estimate air stripper fouling potential.

pH:
Temperature (C)
Total Dissolved Solids (TDS, mg/l)
Ca as CaCO3 (mg/l)
Alkalinity as CaCO3 (mg/l)
Dissolved Iron (mg/l)

Air Strippers Overview

Inorganic Fouling in Air Strippers: Mechanisms and Prevention

Cause

Fouling in air strippers is typically caused by precipitation of inorganic compounds such as hardness (mainly calcium and magnesium), iron and manganese. The hardness of groundwater varies considerably from place to place. Groundwater is commonly classified in terms of the degree of hardness, as follows: soft (0-75ppm), moderately hard (75-150ppm), hard (150-300ppm) and very hard (greater than 300ppm). The occurrence of iron in groundwater at concentrations of 1-10ppm is common; however, higher concentrations of up to 50ppm have been found in some cases.

Air stripping mainly targets the removal volatile organic chemicals (VOCs) from water. In addition to VOCs, carbon dioxide (and other dissolved gases) are also stripped. Stripping CO2 can causing an increase in pH, which increases the formation of the inorganic scale causing solids, noted above.

Prevention

Follow this link for a white paper discussing Options for Prevention and / or Control of Inorganic Fouling in Air Strippers..

Fouling Prediction

One common predictive approach used to predict the tendency of water to be corrosive or scale forming is the the Langelier’s index (LSI). LSI predicts the calcium carbonate stability of water – with the result indicating whether it will tend to precipitate, dissolve or be at equilibrium.

LSI = 0, water is in equilibrium with CaCO3

LSI < 1, water is undersaturated (possible corrosive) and will dissolve CaCO3 (no scale)

LSI > 1, water is supersaturated and CaCO3 will precipitate to form scale

For predictive purposes, -0.5 < LSI < +0.5 indicate that an air stripper is not expected to have significant scale forming.

Fouling Guidelines

The general guideline regarding inorganic fouling in air strippers are as follows:

Hardness <100ppm and/or dissolved Iron<1ppm

Air strippers are expected to operate for a long period of time (over a year). No preventative measures are necessary; however, an annual inspection of the interior of the air strippers is recommended. An acid cleaning may be necessary when appreciable inorganic buildup is found.

Hardness 100-300ppm and/or dissolved Iron 1-5ppm

Air strippers are expected to operate for extended periods between cleanings. Preventative measures are probably not necessary. It is recommended that the interior of the air strippers be inspected every six months. A dilute acid cleaning is recommended when appreciable inorganic buildup is found. Acid selection should take stripper materials of construction into consideration. See this PDF for Acid Cleaning Guidelines.

Hardness >300ppm and/or dissolved Iron >5ppm

Air strippers are expected to require routine cleaning and may foul very rapidly. Some of the preventative and control approaches detailed in the URL link, above are recommended.